1. Field of the Invention
The invention relates to a non-aqueous exhaust process for applying and fixing disperse dyes and/or brightening agents on synthetic polymers.
2. Description of the Prior Art
Substantial advantages in cost, energy and environmental protection may be realized by replacing water with organic liquids in the exhaust dyeing of synthetic polymers. In particular, it is recognized that the energy requirements of such processes are lower than processes employing water, due to the lower specific heats and heats of vaporization of the organic liquids. The chlorinated hydrocarbons, in particular 1,1,1-trichloroethane, trichloroethylene and perchloroethylene, have received considerable attention as organic liquid dyebath media. In order to achieve good exhaust, the dye should possess only slight solubility in the dyebath medium at dyeing temperatures. However, many commercial dyes have appreciable solubilities in the organic solvents commonly employed, thus giving low dye yields (poor exhaust). Improved dye yields have been obtained in such situations by the addition of auxiliary solvents which presumably swell the fibers and facilitate dye penetration into the fibers. Auxiliary solvents also have been employed in conjunction with base solvents in order to bring a difficultly soluble dye into solution. The auxiliary solvent is selected to have a boiling point lower than that of the basic liquid so that on distillation, during a subsequent step of the process, the auxiliary solvent can be distillatively removed, thus decreasing the solubility of the dye in the dyebath medium and improving dye yield (exhaust).
Also known in the art are solutions and dispersions of dyes in liquids of the formula R-F wherein R represents a radical selected from FCl.sub.2 C--CFCl--, Cl.sub.3 C--, Cl.sub.2 CH-- and F.sub.2 ClC--CFCl--. Such dispersions of insoluble or difficultly soluble dyes may be unstable, and it may be difficult or impossible to obtain level dyeings with such dispersions.